This invention relates to improvements in or to an angular velocity sensor for detecting the angular velocity of an object through deflection of a gas flow.
Angular velocity sensors generally called "gas rate sensors" are used in the course adjustment or position control of a ship, an automotive vehicle, etc. Those angular velocity sensors are more resistant to vibrations than gyrocompasses and are capable of detecting the angular velocity of a ship or an automotive vehicle with higher sensitivity and more excellent responsiveness than gyrocompasses.
An angular velocity sensor in general comprises a casing, a sensor body mounted within the casing and including a nozzle and a gas flow sensor composed of thermo-sensitive elements and a cover covering the opening of the casing and forming part of the wall of a pumping chamber defined within the casing. Such angular velocity sensor operates for detecting the angular velocity of an object in which it is mounted, in such a manner that a gas supplied from the pumping chamber is jetted toward the thermo-sensitive elements through the nozzle. A change in the output of the gas flow sensor which is caused by deflection of the gas stream under the influence of angular velocity movement of the object is detected to thereby determine the angular velocity value.
In a conventional angular velocity sensor, the sensor body is comprised of a cylindrical sleeve, a nozzle piece secured to one end of the sleeve and formed therein with a nozzle hole at a diametrical center thereof and a gas flow sensor holder secured to the other end of the sleeve for holding a gas flow sensor composed of a pair of thermo-sensitive elements arranged symmetrically with respect to the diametrical center of the sleeve. A gas flow jetted toward the thermo-sensitive elements through the nozzle hole is deflected due to external angular velocity movement of an object applied to the angular velocity sensor, which results in a difference between the values of radiant heat of the gas stream sensed by the two thermo-sensitive elements. The resulting outputs of the two thermo-sensitive elements are different from each other by an amount corresponding to the actual angular velocity. The angular velocity of the object is thus detected.
Since, as mentioned above, the angular velocity sensors of this kind are adapted to detect the value of angular velocity applied thereto in response to a fine difference between the gas radiant heat amounts which the two thermo-sensitive elements undergo, it is requisite that the axis of the nozzle hole and the center of a line connecting the two thermo-sensitive elements (hereinafter called "symmetrical center") should be in exact alignment with each other to obtain accurate operation of the sensor. However, in the conventional angular velocity sensor, the aforementioned sleeve and nozzle piece are made of separate pieces and further, the gas flow sensor holder is mounted within the angular velocity sensor casing via a separate plate member. Consequently, errors occur in locating these parts during assemblage thereof so that the symmetrical center of the two thermo-sensitive elements and the axis of the nozzle hole are out of alignment, which results in the occurrence of gas turbulences in the space between the thermo-sensitive elements and the nozzle hole, impairing the detecting accuracy of the angular velocity sensor.
Moreover, the conventional angular velocity sensor is composed of many parts. Therefore, it takes much time to assemble and adjust these parts, and accumulated errors occur in locating these parts during assemblage, badly affecting the whole sensor performance.
Further, since detection of the angular velocity value depends upon a fine difference in the gas radiant heat amount which the two thermo-sensitive elements undergo as mentioned above, the gas flow jetted from the nozzle hole should have a perfect streamline shape. To this end, a gas which has a fine molecular size and accordingly is excellent in streamline flow property is conventionally used. However, an ordinary gas sealing method is unable to completely prevent leakage of such small molecular gas from the sensor casing, resulting in that the angular velocity sensor undergoes gas leakage after a long period of use.